Metal oxide nanofibers as filters, catalyst and catalyst support structures.

摘要

For environmental protection, the suppression of automotive exhausts such as nitrogen oxides (NOx) and carbon monoxide (CO) is very important. These gases are potential health hazards and green house gases. Burning of hydrocarbon (HC) ideally leads to the formation of water and carbon dioxide; however, due to incomplete combustion and temperatures fluctuations reached in the combustion chamber, the exhaust contains significant amounts of pollutants which need to be transformed into harmless compounds. Hence this concern triggered the need for stringent environmental regulations which resulted in the introduction of catalytic devices in automobiles.;Traditionally, the catalyst is impregnated onto a porous substrate. The limitation of this method is the difficulty involved in controlling the catalyst particle size during the sintering or reduction steps that result in high temperature agglomeration effects. In the present work, a novel approach has been developed wherein the noble metal nanocatalysts have been incorporated on ceramic nanofibers by the electrospinning process. The catalysts on ceramic nanofibers increase the overall exposed catalyst area and simultaneously immobilize the catalyst to minimize catalyst loss. A small amount of the catalyst incorporated into ceramic nanofibers was mixed with microfibers to fabricate a filter disk by vacuum molding technique. This filter disk termed as 'catalytic filter' is a combination of catalytic elements and filter. The catalyzed ceramic nanofiber augmented microfiber filter media can be used for two applications: reduction of NOx and oxidation of CO and for enhanced particulate removal. This filter would include advantages such as light weight structure, optimization of precious metals, high capture efficiency, high surface area, highly interconnected network of pores and high permeability.;The key aspects in this dissertation can be divided into six parts: fabrication of catalytic filters and their optimization, fabrication of three-way catalysts and oxygen storage catalysts, crosslinking of nanofibers as an intermediate step to ceramic nanofiber manufacture, comparison of catalytic filter with the traditional methods and conventional catalytic converter, particle size reduction and studying the deactivation using water and H2S.;All the types of catalytic filter which were fabricated were successful in reducing NO and oxidizing CO completely. The degradation temperature of NO and CO depended on the type, amount and loading of the catalyst nanoparticles on the alumina nanofiber.